A moving autonomous vehicle, such as a mobile robot, typically includes some type of sensor system for sensing an environment through which the vehicle navigates. Systems employing ultrasonic detectors, mechanical contact devices and laser ranging apparatus are known in the art. Other systems which include a camera to observe the environment and a passive three dimensional image processing system are also known.
A problem associated with traditional three dimensional passive scene analysis vision systems is that such systems require large amounts of computing power. Such systems are also relatively slow and often yield erroneous results. Typically the interpretation of data is too slow to be useful for real time navigation, and may prove erroneous, such as interpreting a shadow as an object, which results in navigation errors. In that the vision system is preferably carried by the robot and is powered by the robot's battery, the size and power consumption of the image processing system are important considerations.
Another problem associated with conventional image analysis systems is related to the often visually "rich" images which the system is required to analyze. For example, in a typical hospital environment a hallway may contain a number of stationary objects, such as laundry carts, meal carts and medical equipment, in addition to a number of moving objects such as employees and patients. In order to navigate rapidly and accurately through such an environment sophisticated and time consuming image analysis techniques are required.
Commercial applications of mobile robots in the service sector include floor cleaning, aids to the handicapped, hospital delivery systems, mail carts, and security. These applications require robust, reliable navigation using sensors which are low in cost and power consumption while providing real-time maneuvering data.
It is therefore one object of the invention to provide a simplification of vision and vision processing for a vehicle, such as a mobile robot.
It is another object of the invention to provide a vision system for a mobile robot, the system requiring a minimum of image processing complexity while yet having an image resolution which is sufficient for guiding the robot through an environment.
It is another object of the invention to provide a vision system for a mobile robot which operates in a high speed manner and which permits the continuous, adaptive motion of the robot through the robot's environment.
It is one further object of the invention to provide a vision system for a mobile robot which analyses a portion of the robot's environment which is relatively visually simple and which is generally free of stationary or moving objects and which further includes a visually distinct reference object or objects.
It is one still further object of the invention to provide a vision system for a mobile robot which views an image of a ceiling disposed above and/or in front of the robot, the vision system inferring navigation related data from the orientation of retroreflective tape on the ceiling.